a trade union which was started in Poland in 1980 by Lech Walesa. Solidarity organized strikes in order to force Poland's Communist government to make political and economic changes. For a time it was an illegal organization and many of its leaders were put in prison. By the late 1980s it had become very powerful, and in 1989 it became the leading party in the new government. Although it later lost power, Solidarity had an important influence on the ending of Communist power in eastern Europe.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.